Surfboard fin having a rearwardly offset bearing surface

ABSTRACT

A fin for a surfboard, having a main body which comprises a first edge which is in contact with the board when the fin is secured to the board, a leading edge at the front and a trailing edge at the rear, a rear curve connecting the leading edge and the trailing edge, the trailing edge comprising a forwardmost front tip. The main body is extended rearwards by an arm which extends from a straight line which is perpendicular to the first edge and passes through the front tip of the trailing edge, as far as the rear curve, the arm having a length greater than approximately 8 cm.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of the U.S. Provisional Application No. 62/045,799, filed on Sep. 4, 2014, the entire disclosures of which are incorporated herein by way of reference.

BACKGROUND OF THE INVENTION

The present invention relates to a fin for a surfboard, as well as to a surfboard having such a fin.

Surfboards generally comprise, towards the rear of the board, one or more fins arranged in vertical planes, comprising, starting from the front, a leading edge forming a convex curve which, as it descends, is inclined rearwards, and then a lower edge substantially forming a tip, and, rising again at the rear, the trailing edge, generally with a concave curve.

The fins constitute vertical planes which, in the longitudinal direction, cut through the water well to reduce drag and braking of the board and, in the lateral direction, offer high resistance, limiting transverse movement.

The surfer can thus control the trajectory of the board, by using his feet to give the board an orientation that will substantially constitute its direction of forward travel.

In general, fins of this type may be found on all types of surfboards for various sports which involve surfing the water.

The fins known in the prior art are relatively compact assemblies with little lateral flexibility, which tends to limit under all circumstances the lateral drift of the rear part of the board.

FIG. 2 shows a first fin 4 comprising a first edge 20 which is up against the underside of a board 2, forming the boundary with the anchoring portion 16.

Starting from the front of the first edge 20, there are, in succession, a leading edge 22 with a rearwardly inclined convex curve, a very short lower edge 24 which touches the horizontal line H at one point, and then a trailing edge 26 of concave curvature which joins up with the first edge 20 at the rear.

There is a first axis of inclination 30, which runs from the center 36 of the first edge 20 to the point of contact 28 between the lower edge 24 and the horizontal line H. A first angle of inclination 32 of this first axis of inclination is thus defined with respect to the axis 0° perpendicular to the upper first edge, which in this example is 45°.

FIG. 3 shows a second fin 4 which is shorter in the longitudinal direction.

The convex curve of the leading edge 22 and concave curve of the trailing edge 26 are more pronounced. In this example, the first angle of inclination 32 of the first axis of inclination 30 is 27°.

Note that in these examples shown in FIGS. 2 and 3, the rear end of the fin 4 forms a rear tip 34 connecting the lower edge 24 and the trailing edge 26. For these types of fin 4, the first angle of inclination 32 of the main axis of inclination 30 rarely exceeds 45°.

FIGS. 4 and 5 show commercially available fins 4 comprising a main body 12 and a rear tip 34 projecting towards the rear of this main body 12, with a large height.

The main body 12 fits inside a main rectangle 40 comprising a short side which corresponds to the first edge 20 of the fin. A second angle of inclination 44 is defined, also called the ‘sweep’ angle, the angle made between the straight line passing through the middle 36 of the first edge 20 and the upper right-hand corner of the main rectangle 40, and the perpendicular axis 0°.

The rear tip 34 fits inside a tip rectangle 46 which adjoins the main rectangle 40. A third angle of inclination 52 is defined, also called the ‘rake’ angle, the angle made between the perpendicular axis 0° and the straight line 48 passing through the rear end 38 of the first edge 20 and the middle 50 of the rear edge of the tip 34, which is in contact with the tip rectangle 46.

For the fin shown in FIG. 4, there is a second angle of inclination 44 of 17° and a third angle of inclination 52 of 40°.

For the fin shown in FIG. 5, there is a second angle of inclination 44 of 17° and a third angle of inclination 52 of 35°.

For the fins shown in FIGS. 4 and 5, the rear tip 34 is somewhat bulky, and has a large height. However, this rear tip 34 directly attached to the main body 12 has a high rigidity in terms of lateral bending, such that the dynamic properties of the fin are quite poor.

SUMMARY OF THE INVENTION

The aim of the present invention is in particular to avoid these disadvantages of the prior art.

To this end it proposes a fin for a surfboard, which is designed to be secured, alone or along with other fins, to the underside of the board, having a main body which comprises a first edge which is in contact with the board when the fin is secured to the board, a leading edge at the front and a trailing edge at the rear, a rear curve connecting the leading edge and the trailing edge, the trailing edge comprising a forwardmost front tip, characterized in that the main body is extended rearwards by an arm which extends from a straight line which is perpendicular to the first edge and passes through the front tip of the trailing edge, as far as the rear curve, the arm having a length greater than approximately 8 cm.

According to the invention, the rear part of the arm forms a bearing surface which is spaced apart from the main body of the fin, which makes it possible to obtain maximum bending between the rear part of the arm and the main body of the fin, which is connected to the board and which is not very flexible. The fin according to the invention provides, when coming out of a turn, a propulsion and acceleration effect. It is possible to modulate the bending of the arm by adjusting the length of the arm, the dimensions, the geometry and the shapes of the bearing surface(s) located at the rear of the arm. According to another advantage, the fin according to the invention makes it possible, owing to the speed and the inclination of the board induced by the surfer in the trajectory, to generate lateral twisting of the arm up to the rear end thereof, along an axis perpendicular to the first edge and passing through the plane of the main body (i.e., perpendicular to the board), which increases control during the turn and which restores propulsion at the end of the trajectory when the surfer releases his weight.

Advantageously, the arm comprises a height reduction, the arm comprising at the rear of the height reduction a bearing surface with a height greater than the height reduction. This feature enhances flexibility.

According to other features, the height reduction is between 2 and 4 cm and/or the bearing surface has a height of between 3 and 5 cm.

Advantageously, the bearing surface is separated from the board by a distance greater than approximately 7 cm.

According to this feature, the bearing surface still performs the function of limiting the lateral drift of the board even when it is well out of the water, for example in jumps. Furthermore, this rear part separated from the board also makes it possible to chase the power of the swell at depth. According to this configuration, the rear part of the arm is positioned outside the turbulence which occurs at the surface or along the board.

Preferably, the arm has a total length of between approximately 10 and 20 cm.

According to another feature, the arm comprises at least one wing at the rear.

Tests have shown that, as wings secured to the rear end of an arm have a degree of lateral flexibility, a dynamic reaction of these wings is obtained, which can give the board propulsion at the end of a turn in small waves. It also provides better control of the trajectory in medium or strong waves, which provides greater reassurance for the surfer by virtue of the increases in speed provided by the fin.

The surfboard fin according to the invention may further comprise one or more of the following features, which may be combined with one another.

In particular, the fin may have a first angle of inclination formed between an axis of inclination passing through the center of the first edge and through a central point of a lower edge of the wing(s), and an axis perpendicular to the first edge, which is greater than substantially 45°.

In particular, the fin may have a second angle of inclination formed between an axis of inclination passing through the center of the first edge and through a point of inflexion of the leading edge, and an axis perpendicular to the first edge, which is greater than substantially 26°.

In particular, the fin may have a third angle of inclination formed between an axis of inclination passing through the rear end of the first edge and through the rearmost point of the rear curve, and the axis perpendicular to the first edge, which is greater than substantially 40°.

Advantageously, the horizontal rectangle starting from the perpendicular line drawn at the rear end of the upper edge, in which the arm and the wings fit, has a length to width ratio of greater than approximately 2. This configuration makes it possible to enhance the dynamic effect of the fin.

In particular, the fin may have a wing projecting downwards from the arm.

According to one embodiment, the fin comprises a wing which is inclined with respect to the plane of the main body of the fin.

The fin may comprise two wings arranged symmetrically with respect to the plane of the main body of the fin. This ensures a degree of resistance of the fin to vertical movements.

Moreover, the fin may comprise a third wing arranged in the plane of the main body of the fin.

The invention also relates to a surfboard having at least one fin according to one of the preceding features.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages will emerge from the following description of the invention, given by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 is a side view of a surfboard comprising a fin according to the invention positioned behind a fin according to the prior art;

FIGS. 2 to 5 show criteria for measuring four fins according to the prior art;

FIGS. 6 and 7 show criteria for measuring two fins according to the invention with a long length;

FIG. 8 shows criteria for measuring a fin according to the invention with a short length;

FIGS. 9a and 9b show the reinforcement by fibers of a fin according to the invention;

FIGS. 10, 11 a and 12 schematically show three types of fins according to the invention as seen from the front, comprising a vertical single wing, an inclined double wing and a triple wing, respectively;

FIGS. 11b and 11c are side and top views, respectively, of the fin shown in FIG. 11 a;

FIGS. 13a, 13b and 13c are, respectively, a schematic view from the front, and drawings seen from the side and from the front, of a fin with an inclined wing;

FIGS. 14a, 14b, 14c are, respectively, side, top and rear views of a fin with a curved double wing;

FIG. 15 is a rear view of a fin with an inclined double wing;

FIGS. 16a, 16b and 16c are, respectively, side, top and rear views of a fin with a flat double wing,

FIG. 17A is a side view of a fin designed to receive removable wings,

FIG. 17B is a top view of wings designed to be mounted on the fin shown in FIG. 17A,

FIGS. 17C and 17D are front views of a fin having wings which are removable, in two configurations.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a surfboard 2 having a front end which is angled upwards so as to surf a wave, and at the rear, in succession along the longitudinal axis, a fin 4 according to the prior art and a fin 10 according to the invention.

The fin 10 according to the invention comprises a front main body 12 which is extended upwards by an anchoring portion 16 which is inserted in the board so as to secure the fin, and has a lower edge extended rearwards by a substantially horizontal arm 14, ending in a wing 18 projecting downwards from this arm.

All of the fins in the figures are shown upside down, with the upper and lower sides of these fins always referring to their position in operation, and not as they appear in these upside down drawings.

FIG. 6 shows a fin 10 in which the leading edge 22 of the main body 12 is extended, after its convex curve, by a lower arm edge 60, which is substantially horizontal. The lower arm edge 60 is extended by a concave curve 62 before continuing through a substantially horizontal lower edge 24 of a wing 18, which is lower.

After the wing 18 is a convex curve, which ascends and continues through the upper arm edge 64, which is also substantially horizontal, before joining the trailing edge 26 at the rear of the main body 12.

Thus, the same vertical plane contains the arm 14 forming a substantially straight structure which extends rearwards, attached to the base of the main body 12, and then the wing 18 descending below this arm, with relatively great lateral flexibility by virtue of the bending of the arm which supports it.

FIG. 7 shows a fin 10 with a shorter arm 14 having a length which is reduced by approximately half with respect to the fin shown in FIG. 6. To give an idea of size, the fin shown in FIG. 6 has an arm with a length greater than or equal to about 50 cm (or 20 inches). The fin shown in FIG. 7 has an arm with a length of less than or equal to about 25 cm (or 10 inches) and preferably between about 10 and 20 cm (about 4 and 8 inches).

As shown in FIG. 7, with the rear end of the arm 14 being shifted rearwards and further away from the main body 12, bending is promoted along an axis substantially perpendicular to the first edge 20, contrary to the variants of the prior art shown in FIGS. 4 and 5 which had only a small bending capacity along an axis substantially parallel to the first edge 20. Such bending along an axis substantially perpendicular to the first edge 20 provides, when exiting a turn, a propulsion and acceleration effect.

Note that the first angle of inclination 32 is 65° for the fin shown in FIGS. 6 and 50° for that shown in FIG. 7, which is greater than the limit of 45° which is not substantially exceeded in known fins 4.

FIG. 8 shows a fin 10 with a second angle of inclination 44 of 27° and a third angle of inclination 52 of 50°.

Thus, the ratio of the surface area of the rear part formed by the arm 14 and the wing 18, inscribed in its rectangle 46, to the surface area of the front main body 12 inscribed in its rectangle 40, is 0.75, the ratio of the third angle of inclination 52 to the second 44 is 1.85, and the ratio of the horizontal side of the tip rectangle 46 to the vertical side thereof, is 2.

The fins 10 according to the invention may be produced by any known method, in particular by machining a blank, for example made of wood, or by molding. It is possible in particular to use composite materials comprising a reinforcement such as glass fibers, carbon fibers or synthetic linen fibers, and a matrix such as a polyester or epoxy resin.

The chosen materials are distributed according to a particular arrangement, in order to obtain the desired flexibility for each part giving the dynamic properties that it is desired to obtain from the fin.

In particular, it is possible to produce the fin from a shaped sheet of composite material, comprising glass fibers pre-impregnated with epoxy resin, enveloped in, as reinforcement, a glass fiber fabric with a density of 600 g/m². After the whole is polymerized, a lightweight, very strong fin is obtained.

FIG. 9a shows a fin 10 comprising carbon reinforcing fibers 70 inside the front main body 12, the fibers culminating in a tip which ends slightly above the lower edge. A degree of flexibility is obtained through this internal reinforcement.

According to another particular feature, in addition to being able to modulate the bending along an axis perpendicular to the first edge 20 thanks to the geometry of the fin, it is possible to modulate this bending by virtue of the nature of the materials used. Thus, FIG. 9b shows carbon reinforcing fibers 72 forming, on either side, a horizontal strip placed on the outside, which extends over the entire length of the fin at the mid height of the arm 14. Good lateral rigidity is obtained by means of these external reinforcements. By way of example, it is possible to thus rigidify fins with a very long arm so as to obtain a bearing surface which is very long and stiff. This particular feature makes it possible to increase the capacity of the board to keep a straight line in very large waves.

FIG. 10 shows a fin 10 comprising a single wing 18 in the same plane as the main body 12 of the fin.

FIGS. 11a, 11b and 11c show a fin 10 comprising a double wing 18 with two downwardly inclined wings 80, forming a ‘V’ in front view.

FIG. 12 shows a fin 10 comprising a triple wing 18 with two wings 82 positioned flat opposite one another, and a third wing 88 in the plane of the main body 12, oriented downwards.

The wings 18 shown in FIGS. 11a and 12 which comprise a horizontal component, give the board a degree of resistance in the vertical direction for keeping it in contact with the water.

FIGS. 13a, 13b and 13c show a fin 10 comprising a wing 90 in which the part arranged below the arm 14 is slightly inclined to the side with respect to the plane of the main body 12. The inclination in this example is 45° with respect to the vertical plane. In general, the inclination may be between 15 and 75°.

A number of particular dynamic effects are obtained, which may be sought with the board shown in the figures.

FIGS. 14a, 14b and 14c show a fin 10 comprising a double wing 18 with two wings 84 fixed horizontally opposite one another at the base of the arm 14, and curved upwards and outwards. This fin design is more particularly suitable for boards for surfing standing up at front of the board (‘nose riding’).

FIG. 15 shows a fin 10 comprising a double wing 18 with two wings 84 fixed opposite one another at the top of the arm 14, forming an upwardly open ‘V’.

FIGS. 16a, 16b and 16c show a fin 10 comprising a triple wing 18 with two wings 82 fixed horizontally opposite one another at the base of the arm 14. The arm 14 arranged in a vertical plane is extended by a boss over part of the length of the wing 18, forming a third wing 88 oriented upwards.

The triple wing 18 thus has a resistance both in the vertical direction with the two horizontal wings 82, and in the horizontal direction with the third wing 88.

Note that for this fin the edges of the arm 14 are rounded, the variable section of this arm narrowing towards the rear.

The horizontal wings provide a counter support at the rear of the surfboard that allows the surfer to position himself at the front of the board, surfing the face of the wave without digging in.

Generally, different shapes of wings may be associated with an arm 14 of suitable length and flexibility in order to obtain a particular dynamic behavior of the board tailored to the skill of the surfer and the sea conditions.

According to another variant shown in FIGS. 17A to 17D, the wings 18 are connected to the rest of the fin in a removable manner For this purpose, the arm 14 comprises a substantially horizontal slot 92 which is open towards the front of the fin. Complementarily, the wing 18 comprises a slot 94 made in a median position, which delimits two wings 96, 96′, and which is open towards the rear of the wing 18. The slots 92 and 94 are dimensioned in such a way as to allow the wing 18 to be assembled to the rest of the fin by nesting.

The wing 18 may be flat or V-shaped, the slot 94 being positioned at the base of the V.

According to this configuration, different wings may be successively secured to the same fin. According to another advantage, the same wing 18 may be secured in different configurations, the edges of the wings 96, 96′ may be oriented downwards as shown in FIG. 17C or upwards as shown in FIG. 17D.

According to a simplified variant, the wing 18 may be integrated into the arm 14.

Whatever the variant, the fin has a main body 12 which comprises a first edge 20 which is in contact with the board when the fin is secured to the board, a leading edge 22 at the front and a trailing edge 26 at the rear, a rear curve 27 connecting the leading edge 22 and the trailing edge 26. According to a feature of the invention, the main body 12 is extended rearwards by an arm 14 which extends from a straight line which is perpendicular to the first edge 20 and passes through the front tip of the trailing edge 26, as far as the rear curve 27, the arm 14 having a length L greater than approximately 8 cm (approximately 3 inches). Preferably, the length L is between 12 and 18 cm (approximately between 5 and 7 inches) in order to obtain a degree of flexibility suitable for the acceleration and driving of the board.

The front tip of the trailing edge 26 corresponds to the rear tip 38 of the first edge 20 in the case of the variants shown in FIGS. 6 and 7. In the case of the variant shown in FIG. 8, the front tip 31 of the trailing edge 26 is shifted towards the front with respect to the rear tip 38.

The length L of the arm corresponds to the dimension of the arm parallel to the first edge 20.

Thus, according to the invention, the rear part of the arm 14 forms a bearing surface connected by the arm 14 to the main body 12 and rearwardly offset, which makes it possible to obtain flexibility along an axis which is perpendicular to the first edge 20 and passes through the plane of the main body 12 (i.e., perpendicular to the board 2).

According to another feature, the arm 14 comprises a height reduction 33, the portion of the arm and/or the bearing surface 35 located to the rear of the height reduction having a height greater than the reduction.

The height of the arm corresponds to the dimension of the arm perpendicular to the first edge 20.

Preferably, the height reduction is of the order of 2 to 4 cm. The bearing surface 35 has a height of between 3 and 5 cm greater than the height reduction.

Advantageously, the bearing surface 35 is separated from the board by a distance greater than approximately 7 cm.

In the presence of a height reduction, the leading edge comprises a point of inflection 29. A point of inflection corresponds to a point at which the leading edge crosses the tangent to the point of inflection. The leading edge 22 may comprise a straight portion, the leading edge having a convex curvature to the front of the straight portion and a concave curvature to the rear. In this case, the point of inflection corresponds to the front tip of the straight portion.

Preferably, a straight line passing through the rear end 38 of the first edge 20 and the point of inflection 29 of the leading edge 22 is perpendicular to the first edge 20.

As is apparent from the foregoing specification, the invention is susceptible of being embodied with various alterations and modifications which may differ particularly from those that have been described in the preceding specification and description. It should be understood that I wish to embody within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of my contribution to the art. 

1-15. (canceled)
 16. A fin for a surfboard, configured to be secured, alone or along with other fins, to the underside of a board, comprising: a main body which comprises a first edge in contact with the board when said fin is secured to the board, a leading edge at the front and a trailing edge at the rear, a rear curve connecting the leading edge and the trailing edge, the trailing edge comprising a forwardmost front tip, an arm extending rearwards from the main body which arm extends from a straight line which is perpendicular to the first edge and passes through the front tip of the trailing edge, as far as the rear curve, said arm having a length greater than approximately 8 cm.
 17. The fin according to claim 16, wherein the arm comprises a height reduction, the arm comprising at the rear of the height reduction a bearing surface with a height greater than the height reduction.
 18. The fin according to claim 17, wherein the height reduction is between 2 and 4 cm.
 19. The fin according to claim 17, wherein the bearing surface has a height of between 3 and 5 cm.
 20. The fin according to claim 17, wherein the bearing surface is separated from the board by a distance greater than approximately 7 cm.
 21. The fin according to claim 16, wherein the arm has a total length of between approximately 10 and 20 cm.
 22. The fin according to claim 16, wherein the arm comprises at least one wing at the rear.
 23. The fin according to claim 22, further comprising a first angle of inclination formed between an axis of inclination passing through the center of the first edge and through a central point of a lower edge of the at least one wing, and an axis perpendicular to the first edge, which is greater than substantially 45°.
 24. The fin according to claim 16, further comprising a second angle of inclination formed between an axis of inclination passing through the center of the first edge and through a point of inflexion of the leading edge, and an axis perpendicular to the first edge, which is greater than substantially 26°.
 25. The fin according to claim 16, further comprising a third angle of inclination formed between an axis of inclination passing through the point where the trailing edge joins the first edge and the rearmost point of the rear curve, and an axis perpendicular to the first edge, which is greater than substantially 40°.
 26. The fin according to claim 16, further comprising a rectangle, one of the sides of which coincides with a straight line which is perpendicular to the first edge and passes through a point where the trailing edge joins the first edge, in which the arm and any wings are inscribed, said rectangle having a length to width ratio of greater than approximately
 2. 27. The fin according to claim 16, further comprising a wing which is inclined with respect to the plane of the main body.
 28. The fin according to claim 16, further comprising at least two wings arranged symmetrically with respect to the plane of the main body.
 29. The fin according to claim 28, further comprising a third wing arranged in the plane of the main body.
 30. A surfboard having at least one fin configured to be secured, alone or along with other fins, to the underside of a board, the at least one fin comprising: a main body which comprises a first edge in contact with the board when said fin is secured to the board, a leading edge at the front and a trailing edge at the rear, a rear curve connecting the leading edge and the trailing edge, the trailing edge comprising a forwardmost front tip, an arm extending rearwards from the main body which arm extends from a straight line which is perpendicular to the first edge and passes through the front tip of the trailing edge, as far as the rear curve, said arm having a length greater than approximately 8 cm. 